An installation of a wind turbine on offshore sites is expensive and time consuming, as the components of the wind-turbine, which are huge and heavy, have to be loaded separately by the help of a huge crane on a ship, have to be transported to the offshore site and have to be mounted there by the help of a ship-crane.
These wind-turbine components comprise especially the tower itself, the blades and the nacelle, where the nacelle is already connected with the hub normally.
If there is bad weather at the offshore-site or if there is a strong wind-situation, it is very difficult to install and mount the wind-turbine components. Especially the large blades, which show a big wind-load while mounting, lead to a difficult installation of the blades to the hub.
The EP 1 518 053 B1 shows a method to install wind-turbine components. A nacelle, tower modules and a jacking-crane are unloaded from a ship at an offshore foundation by help of a ship-crane. The tower modules are installed by help of the jacking crane. Then each blade is unloaded from the ship by help of the ship crane and is handled to the jacking crane on the tower. The blades are installed by lifting each blade up to the nacelle for attachment by the jacking crane. This method is very time-consuming.
The EP 1 101 936 B1 describes a method to install blades to the hub of a wind-turbine by using a winch with a wire. The winch is placed in the nacelle while the wire is going out through the hub and is attached to each of the blades for the installation. This method is also very time-consuming.